Studies of Thermal Imidization Kinetics of Polyisoimide Based upon 4,4′-[1,4-Phenylenebis-(1-methyl ethylidene)] Bisaniline and 4,4′-Oxydiphthalic Anhydride in Solid State

The curing kinetics of the polyisoimide (BIS-P/ODPA), based upon 4,4′-[1,4-phenylene-bis-(1- methyl ethylidene)] bisaniline (Bis-P) and 4,4′-oxydiphthalic anhydride (ODPA), was studied by differential scanning calorimetry (DSC). The glass transition temperatures of the partially imidized polyisoimides (Bis-P/ODPA) were measured by DSC as a function of fractional conversion. The thermal imidization of polyisoimides in the solid state showed a maximum degree of imidization that can be achieved at a given isothermal temperature probably due to the diffusion-controlled reaction characteristics near vitrification (T _g effect). Dynamic curing studies were performed at different heating rates of 1, 2, 5, 10, 15, 20, 25, 30°1. These data were analyzed for obtaining the activation energy and pre-exponetial value for the imidization reaction. The thermal imidization was well described by first-order kinetics with activation energy of 181-202 kJ mol⁻¹ and the pre-exponential factor of 36-40 min⁻¹.